Re: [RFC PATCH 05/11] target/arm: Introduce arm_hw_accel_cpu_feature_supported()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 12/8/25 02:35, Richard Henderson wrote:
> On 8/12/25 03:06, Philippe Mathieu-Daudé wrote:
>> Introduce arm_hw_accel_cpu_feature_supported() helper,
>> an accelerator implementation to return whether a ARM
>> feature is supported by host hardware. Allow optional
>> fallback on emulation.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   target/arm/cpu.h     | 12 ++++++++++++
>>   target/arm/hvf/hvf.c | 20 ++++++++++++++++++++
>>   target/arm/kvm.c     | 22 ++++++++++++++++++++++
>>   3 files changed, 54 insertions(+)
>>
>> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
>> index dc9b6dce4c9..5136c4caabf 100644
>> --- a/target/arm/cpu.h
>> +++ b/target/arm/cpu.h
>> @@ -2507,6 +2507,18 @@ static inline ARMSecuritySpace 
>> arm_secure_to_space(bool secure)
>>   }
>>   #if !defined(CONFIG_USER_ONLY)
>> +
>> +/**
>> + * arm_hw_accel_cpu_feature_supported:
>> + * @feat: Feature to test for support
>> + * @can_emulate: Whether Allow to fall back to emulation if @feat is not
>> + *               supported by hardware accelerator
>> + *
>> + * Hardware accelerator implementation of cpu_feature_supported().
>> + */
>> +bool arm_hw_accel_cpu_feature_supported(enum arm_features feat,
>> +                                        bool can_emulate);
> 
> internals.h.
> 
> I guess this is ok.  If we ignore xen, which is a thing of its own, we 

Does Xen manage vCPUs runtime?

> don't currently have more than one accelerator per OS.  That hasn't 
> always been true for x86, where we had 2 or 3 at once for Windows.

I felt than adding as per-target per-accel methods would be over
engineering at this point, but I can give it a try if preferred.